Compositions having isocyanate functional components are utilized to bond substrates together. One common use of such compositions is to bond glass, often in the form of windows, into structures. In automotive assembly plants windows are often bonded in with one part adhesive compositions containing isocyanate functional components. Typically these compositions cure by reaction with ambient moisture. One part adhesives are used because the equipment required to dispense and apply the adhesives are less complex than the equipment used to apply two-part adhesive compositions. The one part moisture curing adhesives typically take several hours to cure. In the assembly plant environment, vehicles are not driven for several hours and this slow curing process is acceptable. One part moisture curing adhesives known in the art are disclosed in U.S. Pat. Nos. 4,374,237, 4,687,533, 4,780,520, 5,063,269, 5,623,044, 5,603,798, 5,852,137, 5,922,809, 5,976,305, 5,852,137 and 6,512,033, relevant portions incorporated herein by reference. Examples of commercial one part adhesives include BETASEAL™ 15630, 15625, 61355 adhesives available from The Dow Chemical Company, EFBOND™ windshield adhesives available from Eftec, WS 151™, WS212™ adhesives available from Yokohama Rubber Company, and SIKAFLEX™ adhesives available from Sika Corporation.
Two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components in the other part are used in situations where cure speed is important. One such environment is in the automotive aftermarket replacement glass business. Often customers desire that the adhesive cures quickly so that the vehicle can be driven as soon as possible after bonding of the replacement window into the vehicle. The advantage of a two-part adhesive is that the curing reaction proceeds at a much faster reaction rate than does a one part moisture curing adhesive system. Examples of two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components in the other part are disclosed in EP 1,524,282, U.S. Pat. Nos. 5,852,103, 6,709,539, 7,101,950 and 7,361,292, relevant parts incorporated herein by reference.
Adhesives are utilized in bonding of large windows into large transportation vehicles such as train cars and engines, busses and large trucks. The mass of these windows creates a need for adhesives which have a unique set of properties. In particular adhesives which have a good green strength shortly after application are needed, typical one part adhesives do not provide such green strength properties. Further, the adhesive systems need a longer open time, the time from application of the adhesive to a substrate until the adhesive can no longer adhere to a substrate, than a typical two-part adhesive allows. An open time of between 15 minutes and 30 minutes is desired. Thus, what is needed is a two-part adhesive system which exhibits a good green strength, that has the capability to hold a large mass window in place upon application and a longer open time to allow for slower sealant application and assembly process and for possible adjustment of the window after contacting the window with a window frame.